What is the difference between $.map and $.grep in jQuery

What i开发者_JAVA技巧s the difference between $.map and $.grep in jQuery?

I want a simple answer as far as possible.

I will assume you mean $.grep and $.map. The difference is that we use $.grep to filter an array while we use $.map to apply a function to each item in the array.

Here is a much better explanation than I can make:

http://onwebdev.blogspot.com/2011/03/jquery-grep-and-map-example-and-syntax.html

$.map method can be used as an iterator, but is meant to manipulate the array and return a new array.

var items = ['A','B','C','A'];    

var items = $.map(items, function(item) {
  if (item == 'A') 
    return null;
  return item;
});

items is now new array. ['B','C']

or

var items = $.map(items, function(item) {
  if (item == 'A') 
    return 'A'+'B';
  return item;
});

output will be ['AB', 'B', 'C', 'AB']

$.grep is used for filtering

var items = $.grep(items, function(item) {
      return item != 'A';
    });

items is now ['B','C']

however

var items = $.grep(items, function(item) {
      if (item == 'A') 
        return 'A'+'B';
      return item;
    })

will return ['A', 'B', 'C', 'A'] as it is not producing new stuff - it reduces the existing.